This research project has three specific goals for the coming year. First, we will completely characterize the primers at the E. coli replication fork using cellophane disc lysates. We have found RNA priming to be non-sequence specific and flexible. Second, we will study the specificity of the 5' yields 3' exonuclease of DNA polymerase I. We have examined a specific nick in phi X174 and found that the exonuclease does not necessarily cleave every displaced phosphodiester bond during nick translation. Finally, we plan to study to structural requirements for DNA activation of the eukaryotic enzyme poly ADPR synthase.